The present invention relates to a semiconductor device, for example, a technology preferably used for a semiconductor device using a nitride semiconductor.
A nitride semiconductor such as gallium nitride (GaN) is expected to be used for transistors for high breakdown voltage, high output, or high frequency because of a band gap and electron mobility greater than those of silicon (Si) or gallium arsenic (GaAs). Power control field effect transistors, that is, power devices using a nitride semiconductor such as gallium nitride have therefore been under development.
Japanese Patent Laid-Open No. 2005-183551 (Patent Document 1) and Japanese Patent Laid-Open No. 2005-244072 (Patent Document 2) describe a technology relating to a field effect transistor using gallium nitride as a nitride semiconductor layer. The field effect transistors described in Patent Documents 1 and 2 have a channel layer, a barrier layer formed on the channel layer, and a gate electrode formed on the barrier layer.    [Patent Document 1] Japanese Patent Laid-Open No. 2005-183551    [Patent Document 2] Japanese Patent Laid-Open No. 2005-244072